The present invention relates to a device for controlling fuel combustion in a burner of a heater for a motor vehicle.
The passenger compartment or cabin of a motor vehicle is generally heated by a heat source employing the cooling water of the internal combustion engine of the motor vehicle. However, in cold weather, it takes time to increase the temperature of the cooling water, and hence the compartment cannot be heated quickly.
Japanese Laid-Open Patent Publication No. 61-157422 discloses a vehicle heater device in which fuel is combusted by a burner separate from the internal combustion engine and heat generated by the fuel combustion is recovered by a heat exchanger to supply heating air into the compartment. The heater device includes a fuel atomizer disposed in the burner for atomizing fuel, the fuel atomizer having an atomizing glow plug which is kept at a prescribed temperature.
An experiment conducted by the inventor indicates that fuel is atomized by the fuel atomizer in different conditions dependent on the temperature of the fuel atomizer including the atomizing glow plug, and cannot be sufficiently atomized if the temperature is excessively high. More specifically, if the temperature of the fuel atomizer including the atomizing glow plug is too high, supplied fuel is set off upon abrupt conversion from the liquid phase to a gaseous phase at the instant the fuel contacts the heated glow plug of the fuel atomizer, and is separated from the glow plug as large fuel droplets. Therefore, the fuel cannot be well atomized and hence cannot be well ignited subsequently.